The present invention is concerned with rotating machines and relates more particularly to energised reluctance machines.
In the context of electromechanical energy storage, electric machines acting as motors and generators are generally conventional structures (synchronous with permanent magnets or asynchronous).
The combination of the storage function, properly so called, which is provided by an inertia wheel, with the motor/generator function is effected in two ways:
xe2x80x9cdecoupledxe2x80x9d, where the motor/generator corresponds to a component of the most conventional topology, which is simply added on;
xe2x80x9cintegratedxe2x80x9d, where the machine forms part of the inertia wheel. In that case too, the machines used are relatively conventional in design.
With regard to the topologies used, they may be as follows:
pure variable reluctance synchronous machine, with a radial magnetic field and coil in the air gap, guiding of which is effected by ball bearings assisted by magnetic bearings (for example the xe2x80x9cActive Powerxe2x80x9d system);
synchronous machine having permanent magnets with a radial or axial field and with a coil in the air gap or with a coil in slots (various constructions);
asynchronous machine with a coil in slots and a solid rotor (for example the xe2x80x9cJapanese Flywheelxe2x80x9d system).
Those topologies do not have adjustable energisation, and certain ferromagnetic elements are fixed. Such topologies therefore have three major disadvantages:
the existence of losses on no-load operation (storage operation), leading to substantial self-discharge (except for the asynchronous machine and the pure variable reluctance machine);
low flexibility of adjustment of the energy exchanges by adjustment of the induction current;
poor efficiency at low charge.
The object of the invention is to provide an electromagnetic motor/generator for the electromechanical storage of the electrical energy with very high efficiency, especially with low self-discharge, which can be integrated with an inertia wheel.
To that end, the machine must simultaneously satisfy the following criteria:
small losses on no-load operation, that is to say operation without current, which must be manifested in an absence of magnetic losses in the iron and in the coil and very few mechanical losses,
no losses at the rotor despite the high rotational speeds (peripheral speed close to that of the inertia wheel),
no disturbance of the magnetic bearings by parasitic forces,
independent adjustment of the excitation flux for better control of the energy exchanges and a better power factor (minimum apparent power of the associated electronic converter),
good integration with an inertia wheel.
The invention accordingly relates to an electric machine forming a motor or generator, comprising a fixed part and a movable part, in which one of the fixed and movable parts is passive and comprises two elements of ferromagnetic material which define between them a regular interval, said elements being connected to one another by a joining element which is likewise made of ferromagnetic material, and the other of said fixed and movable parts comprises a multiphase armature coil, which generates a shifting field, as well as a centralized field coil supplied by a direct current, said armature coil and field coil being arranged in an air gap defined by the regular interval, characterized in that at least one of said elements of ferromagnetic material is provided with openings.
According to other features:
the rotor is a passive rotor comprising two coaxial elements of revolution which are made of ferromagnetic material and at least one of which is provided with openings, which elements are connected to one another by a joining element which is coaxial with respect to the two elements of revolution and is likewise made of ferromagnetic material, and the stator comprises, arranged in an air gap defined by the regular interval formed between the two elements of revolution, a fixed armature coil, which generates a rotating field, and a field coil, which is likewise fixed,
all the ferromagnetic elements are rotating,
the rotor is composed of two ferromagnetic disks, at least one of which is toothed,
the rotating disks are fixed on a shaft of ferromagnetic material,
the fixed armature coil and the fixed field coil are arranged in the space between the disks,
the armature coil is a multiphase coil whose phases are arranged in the same plane or according to superposed planes in the air gap formed by the rotating toothed disks,
the phases of the armature coil are formed by turns which are offset angularly and are distributed regularly along the periphery of the machine,
the field coil is arranged about the shaft and is surrounded by the armature coil,
the field coil is a fixed global coil in the form of a solenoid,
the rotor comprises a shaft surrounded by two coaxial cylinders of ferromagnetic material which are provided with teeth and cut-outs distributed regularly at one of their ends, and a joining flange of ferromagnetic material,
the rotor comprises a shaft surrounded by two cylinders of ferromagnetic material which are provided with holes distributed regularly at one of their ends, and a joining flange of ferromagnetic material,
the inner cylinder of ferromagnetic material is in one piece with the shaft of the rotor,
the fixed part comprises a rail of ferromagnetic material having lateral walls provided with openings distributed regularly over its length, and the movable part comprises a support of non-magnetic material carrying an armature coil and a field coil which are arranged in an air gap defined by the regular interval between the lateral walls,
the openings provided in the lateral walls of the rail are cut-outs separating teeth of said rail,
the openings provided in the lateral walls of the rail are holes formed at regular intervals in said lateral walls.